The present invention generally relates to working machines, and more particularly to feed devices that act on components.
The machining of large machine shafts, for example turbine and generator shafts, requires special lathes for which large machine sheds are necessary. For working on site, for example for machining the bearing seats during repair by lathe-turning, grinding or polishing, it would be desirable to carry out machining by way of nonstationary machines which can be placed onto the stationary shaft, so that extensive and costly demounting and transport work could be avoided. Even possible damage to the shaft as a result of transport to the place of use itself and also during subsequent installation work often make additional work on the shaft desirable.
For uses on smaller shafts, lathes are already known which are placed onto a shaft and rotate around the shaft. The problem of such machining appliances is the generation of advance movements for the machining tools in a longitudinal direction and transversely to the shaft. Separate drives which corotate with the lathe have to be used for generating the advancing movements. Apart from the large mass which has to be moved and supported in this way, thus causing vibrations which lead to machining inaccuracies, such an arrangement has further disadvantages. The energy for these drives has to be transmitted to the rotating drives by way of slip rings. The working machine must therefore have an unsplit design, since the slip rings would otherwise also have to be split, but power transmission via split slip rings would present considerable technical difficulties.
It is desirable, by contrast, for a working machine to be designed to be splittable in order to be placed onto a correspondingly large shaft and for the working machine to be assembled for a machining operation on the shaft, though without requiring power transmission via split slip rings. Moreover, the rotating mass is to be kept as small as possible.
A feed device is disclosed in JP-A 62287907, in which the drives for the advancing movements are likewise arranged at a fixed location. The advancing movements take place via the relative movement of a further transmission mechanism cooperating with the respective leadscrew, in addition to the main transmission mechanism. These transmission mechanisms are connected to the main transmission mechanism in each case via a planetary gear, the planet wheels of which can be additionally driven or braked by rest motors and consequently bring about the relative movement. The solution has the disadvantage that planetary gears of this type are highly cost-intensive, and that, particularly in the case of run-on and run-off ramps, internal forces occur which lead to unintended relative movements of the main drive and advancing drive and consequently to unintended adjustments of the machining tools.
An object on which the present invention is based is to specify a method for carrying out the advancing movement and a feed device for a working machine with a rotating tool support the method and the feed device allowing machining (lathe-turning, milling, orbital grinding) in NC quality.
The object is achieved by exemplary non-limiting embodiments of the present invention.
The advancing movement of the tools is generated in that transmission mechanisms are provided, which drive the leadscrews of the tool supports and are themselves driven at a different speed from the working machine which rotates as a whole; the relative speed between the two then takes effect.
If the relative speed is zero, no advancing movement takes place.
Preferably, a plurality of large gear rings are provided as transmission mechanisms between the drive motors and the working machine. One of these gear rings is provided for rotating the entire working machine and consequently also determining the cutting speed of a tool with respect to the shaft, while the other gear ring, or gear rings, serves for the advancing movements of the tools.
When all the gear rings rotate at the same speed, no movement takes place on the cross slide and longitudinal slide supports. Only when the gear rings for the supports for longitudinal and cross movement run more quickly or more slowly than the gear ring driving the working machine, is there a rotation of the leadscrews and therefore an advance of the supports in relation to the working machine on account of the relation movement between the gear rings. It is therefore necessary to drive the support motors, which act on the individual gear rings, more quickly or more slowly than the gear ring for the working machine when an advancing movement is to be brought about.
There is a drive motor in each case for driving the gear ring of the rotating working machine and that of the leadscrews. In order to drive all the gear rings synchronously with the main motor in an operating phase in which no advancing movement is to take place, according to the present invention, a mechanical coupling of the main motor to the support motors is provided; for example, via toothed belts, via which the housings of the support motors are taken up by the main motor. Specifically, in the case described here, at the same rotational speed, the shafts of the support motors, which are not themselves driven in this operating phase, also being taken up at the same rotational speed and driving the gear rings for the leadscrew movement, so that there is no movement of these gear rings in relation to the gear ring which brings about the rotational movement of the entire working machine. In order at the same time to rule out the effect of internal forces in the working machine, each support motor is expediently braked in this operating phase.
All the drive motors are arranged at a fixed location, for example directly on the stationary shaft or on a block standing next to the shaft. In this case, the tools controlled by the leadscrews rotate together with the working machine, without executing a relative movement perpendicularly to or along the shaft, as long as the rotational speed of the motor shaft of one or both support motors is not changed in relation to the rotational speed of the driving main motor. Only when, as a result of the switched-on specific drive movement of one of the support motors, one leadscrew or another rotates more quickly or more slowly than the working machine, about the shaft to be machined, is there a movement of the tool or tools in relation to the shaft. The supply of power to the support motors, the housings of which are fixed in place, but rotate at the same rotational speed as the main motor, takes place via slip rings. The voltage supplied via the slip rings determines the rotational speed of the respective support motor and consequently the advancing speed.
Instead of lathe tools, other tools may also be used for machining the shaft surface, such as, for example, grinding wheels, milling cutters or polishing devices.
It is assumed above that all the gear rings and the pinions driving the gear rings have the same diameters and numbers of teeth, and the main motor and the housings of the support motors have the same rotational speed. This is certainly the most practical solution. It is also possible, however, to use gear rings with different diameters, when the pinions likewise have different diameters and/or the rotational speeds of the motors are not identical. It is important merely that, in the operating state in which no advancing movement is to take place, all the gear rings are driven at the same rotational speed.
The solution has the advantage that the working machine may have a split design. All the drive motors are to be arranged at a fixed location, and the support motors do not corotate with the entire machine, but only independently. The rotating mass is therefore also kept small. The power transmission to the support motors may be carried out via unsplit slip rings. A simple and accurate control of the tool supports becomes possible, even in the case of run-on and run-off ramps, and during curve machining of a component to be machined. That is to say surfaces, diameters and curves may be machined, programmed, by way of the NC technique, as in conventional machine tools.